Building system and method

ABSTRACT

A building system comprising insulating formers manufactured from an insulating material, for example polystyrene foam. Each former has at least one internal wall defining a rebated portion in which concrete can be cast, forming a reinforcing rib. The rebated portion typically has a dove-tail profile to reduce the likelihood of the cast concrete rib falling out. Each former has locating formations or engagement means configured for complementary engagement with at least one other former, allowing the formers to be arranged in register with one another. Also disclosed is a method of building which includes the steps of: shaping formers from insulating material, for example polystyrene foam, in such a way that the formers each define a rebated portion and engagement means configured for complementary engagement with at least one other former; casting reinforced concrete ribs in the rebated portions; and arranging the formers in abutment with one another.

TECHNICAL FIELD

THIS INVENTION relates to a building system and method. It relates in particular to a building system and method involving insulating formers.

BACKGROUND ART

According to conventional techniques used for many years in the background art, concrete is poured into site-specific formers and cured on site. Also known in the background art is structural precast concrete, which is a construction product produced by casting concrete in a reusable former, curing it in a controlled environment, transporting it to the construction site and lifting it into place.

Insulating Concrete Form (“ICF”) is a system of formwork that stays in place as permanent building insulation for cast-in-place, reinforced concrete walls, floors and roofs. In conventional systems of ICF, forms consisting of insulating material are placed on either side of the volume which is to be concreted, forming two, spaced walls, and concrete is poured between the walls. The insulating forms are left in place permanently after casting.

There are disadvantages with conventional systems of ICF. The cost can be higher than with traditional building methods. Also, adding or moving doors, windows, or utilities is difficult once the building is complete (concrete cutting tools may be needed).

A building system is needed which is more suited for construction of low-cost housing, and which allows more versatile construction and modification than existing systems of ICF.

DEFINITIONS

For purposes of this specification, the term “polystyrene” includes reference to expanded or extruded polystyrene foam, i.e. expanded or extruded poly(1-phenylethene-1,2-diyl)).

The term “rebar” serves as an abbreviation for reinforcing bars or reinforcing steel rods of the kind which are typically used in combination with concrete to form reinforced concrete.

The term “slab” is intended to be interpreted broadly. Apart from its usual meaning, referring to a flat layer of concrete laid or cast in situ with or without reinforcement, the term also includes reference to a layer of floor panels or roof panels covered with a concrete topping.

DISCLOSURE OF INVENTION

According to a first aspect of the invention there is provided a building system which includes

a plurality of separate, insulating formers, each former comprising

a body portion manufactured from an insulating material and having at least one internal wall which defines a rebated portion in which concrete can be set, thereby to form a reinforcing rib; and

engagement means or locating formations configured for complementary engagement with at least one other former, thereby to facilitate alignment of the formers in register with one another, in use.

The insulating material may include an expanded or extruded polymer foam. Typically the insulating material is selected from the group consisting of polystyrene foam and polyurethane foam.

The building system may further include at least one concrete rib set in the rebated portion of at least one of the formers. The concrete rib is typically reinforced, for example with rebar, mesh, lattice reinforcement, or the like, depending upon the application.

The internal wall or walls defining the rebated portion of the, or each, former may further define a mouth which opens into the rebated portion. To hold a concrete rib securely within a former after the concrete has set, each former is preferably preconfigured so that the shortest distance from one side of the mouth to the other is shorter than at least one parallel dimension of the rebated portion. In other words, the mouth may be configured to be narrower than the interior of the rebated portion thereby helping to hold the set concrete in place and reduce the likelihood of it from falling out of the relevant former.

Preferably the internal walls slope away from the mouth thereby defining a rebated portion with a dove-tail cross-section. In use, this shape is imparted to the concrete rib formed in the rebated portion, which helps to stop the rib from falling out of the former.

The insulating formers and concrete ribs may, in combination, form structural units. The structural units may be selected from the group consisting of wall panels, infill wall panels, cladding panels, roof panels, suspended slab panels, floor panels, lintels, posts, beams, columns, staircases and the like.

In another aspect of the invention there is provided a building when constructed using the building system described above.

According to a further aspect of the invention there is provided an insulating former for use in a system of building, the insulating former comprising

a body portion manufactured from an insulating material and having at least one internal wall which defines a rebated portion in which concrete can be set, thereby to form a reinforcing concrete rib; and

engagement means or locating formations configured for complementary engagement with at least one other former, thereby to facilitate alignment of the formers in register with one another, in use.

In another aspect the invention provides a structural unit which includes an insulating former as described herein, and a concrete rib cast in its rebated portion.

In a related aspect there is provided a building which includes a plurality of structural units as described above, each aligned in abutment with at least one other of the structural units.

The building may include primary construction components selected from the group consisting of walls, infill walls, cladding, suspended slabs for roofs, suspended floors, beams, staircases, columns and lintels, each of such primary components comprising at least one structural unit as described herein.

The structural units may be selected from the group consisting of wall panels, infill wall panels, cladding panels, roof panels, suspended slab panels, floor panels, lintels, posts, beams, columns, staircases, doors and the like.

At least two of the structural units may share a common reinforcement member cast into the concrete of each of said units. For example, a structural unit in the form of a wall panel may be connected to a structural unit in the form of a suspended floor slab by a common reinforcement rod cast into the concrete forming the rib of the wall panel and also cast into the concrete forming the suspended floor slab.

The building may include at least one wall having at least one lintel supported thereon, said lintel comprising at least one insulating former and a continuous reinforced concrete rib cast into the former and extending substantially the full length of the wall.

At least one of the lintels may define sloping upper edges and may have the general configuration of a gable.

The building may include a plurality of lintels arranged non-linearly and connected to one another by the continuous concrete rib, at least one of the formers defining mitred engagement means for engagement with at least one abutting lintel.

The building may include at least one bunk bed mounted on a plurality of the wall panels. Typically the bunk bed is mounted on the concrete ribs of said wall panels.

The building may include a roof comprising a plurality of roof panels. The concrete ribs of the roof panels may be reinforced with elongate lengths of lattice reinforcement. The roof panels may be supported by at least one suspended support beam. The beam may be a reinforced concrete support beam cast in situ during casting of the concrete ribs of the roof panels, and may be continuous with such concrete ribs.

The roof may include generally flat portions and/or pitched or sloped portions. In the case of a pitched roof (or portions thereof) the roof panels may be inclined to the horizontal at an angle lying the range from 1° to 30°, preferably 8° to 16°, most preferably approximately 12°.

The building may include a roof reservoir comprising a plurality of roof panels, a concrete topping cast thereon, and at least one end wall or shutter. The end walls may be provided by copings. The copings may be manufactured from a polymer foam such as expanded or extruded polystyrene foam and may define at least one profile having aesthetic features.

The roof reservoir is typically fitted with a tap.

The building may comprise a frame structure (for example a concrete, steel or wood frame structure) with infill walls or cladding extending between parts of the frame structure. The infill walls may comprise structural units as proposed herein, for example infill wall panels. The infill wall panels may be connected to the parts of the frame structure, e.g. to upper and lower slabs, by fastening means. The fastening means preferably comprise brackets, each bracket defining a generally right angled profile, and fasteners for connecting the brackets to the infill wall panels and the frame parts. The term “infill wall panel” as used herein includes reference to cladding panels used in the context of a concrete frame structure.

The building may be a high-rise building.

According to a further aspect of the invention there is provided a pre-fabricated, mobile structure having a roof and floor connected by walls;

the roof, floor and walls each including a plurality of structural units as herein described; and

said structure being loosely mounted on the ground in a manner permitting tool-free movement of said structure.

The invention also provides an intermediate stage or structure of a building, said intermediate structure comprising a wall fastened to a temporary support structure held up by stands, the wall including a plurality of structural units as herein described. Typically the support structure extends the full length of the wall and the wall is fastened to it by means of wire ties tied onto reinforcement bars projecting up from the wall.

According to a further aspect of the invention there is provided a door which comprises at least one sheet of insulating material embedded in a concrete mix. A portion of the concrete mix may include a plurality of aggregate elements manufactured from an insulating material. The insulating material of the sheet (and of the aggregate elements) may be selected from the group consisting of polystyrene foam, polyurethane foam and recycled products of these materials. For example, the sheet or sheets of insulating material may be manufactured from recycled polystyrene and the aggregate elements in the concrete mix may include recycled polystyrene beads.

The door may further include at least one functional component selected from the group consisting of hinges and a lock mechanism, cast into the concrete mix.

According to yet another aspect of the invention there is provided a method of building which includes the steps of

shaping an insulating material to define a plurality of insulating formers, each former defining a rebated portion and engagement means for engagement with at least one other former;

laying reinforcement into the rebated portion of each former;

pouring, packing or otherwise placing concrete into said rebated portions of the formers and allowing it to set, thereby to manufacture a structural unit from each said former; and

arranging at least two of the structural units so manufactured in abutment with each other.

According to a related aspect of the invention there is provided a method of building which includes the steps of

shaping an insulating material to define a plurality of insulating formers, each former defining a rebated portion and engagement means for engagement with at least one other former;

arranging at least two of said insulating formers in abutment with each other;

laying reinforcement into the rebated portion of each former; and

pouring, packing or otherwise placing concrete into said rebated portions of the formers and allowing it to set, thereby to form abutting structural units.

In the latter method the concrete may be poured, packed or placed to a depth sufficient to form a concrete layer above the formers. This layer may then cure to establish a composite slab consisting of a concrete topping bound to the formers beneath.

The insulating material may include an expanded or extruded polymer foam. Typically, the insulating material is polystyrene foam.

The step of shaping the insulating material may include a further step of shaping a mouth which opens into the rebated portion, and dimensioning the mouth such that the shortest distance from one side of the mouth to the other is shorter than at least one parallel dimension of the rebated portion.

The method of building may include at least one further step selected from the group consisting of:

manufacturing a concrete footing by placing at least one elongate slot-former above a concrete base and casting concrete on either side of it, thereafter removing the slot-former to define a slotted footing and inserting structural units into said slotted footing;

projecting reinforcement from the structural units and connecting at least two of the structural units by means of the reinforcement;

projecting reinforcement from the structural units and casting a concrete slab around said reinforcement; and

fastening at least one fixture to at least one of the structural units.

The elongate slot-former may be manufactured from a polymer foam, preferably an expanded or extruded polystyrene or polyurethane foam.

In the step of projecting reinforcement from the structural units and casting a concrete slab around said reinforcement, the reinforcement may be projected operatively generally horizontally from the wall panels above and below a proposed suspended floor slab, and cast into said slab. Optionally, elongate brace means, for example a tie rod or strut, may be mounted extending between the slab and at least one of the wall panels above and below the slab.

In the step of fastening a fixture to at least one of the structural units, the fixture to be fastened may, without limitation, be selected from the group consisting of: a bed, an appliance, a light fitting, an entertainment device, an electrical fitting, a plumbing fixture, a mirror, an in item of sanitaryware, an item of kitchenware, a furniture item, a shelf, an appendage, and an apparatus.

In an aspect of the invention relating to construction by means of frame structures, the method of building may include the steps of:

providing a frame structure (for example a concrete, steel or wood frame structure);

erecting structural units as described herein extending between parts of the concrete frame structure; and

fastening the structural units to the frame structure.

The structural units may be infill wall panels. The frame structure may include concrete slabs, for example suspended floors, and the structural units may be erected generally vertically, extending between these slabs.

The step of fastening the structural units to the frame structure may include fastening at least one bracket to each structural unit and to the frame structure by means of fasteners. Each bracket typically defines a generally right angled profile.

The frame structure may be the frame structure of a high-rise or multi-storey building.

The method of building may include the following steps for constructing a pitched roof:

supporting a plurality of insulating formers of the type described herein at a pitched angle to the horizontal, each abutting at least one other of the formers (typically interlocking with it);

during the step of laying reinforcement into the rebated portion of each former, laying lattice reinforcement into said portions; and

-   -   during the step of placing concrete into the rebated portions of         the formers, placing the concrete over the formers to a depth         sufficient to form a concrete layer above the formers.

The angle to the horizontal at which the formers are supported may lie in the range from 1° to 30°, preferably 8° to 16°, most preferably approximately 12°.

The formers may be supported on load-bearing structural members and/or temporary supports. The formers may be supported at one end on a reinforced concrete beam. The beam may be cast in situ during the placing of the concrete over the formers.

The invention extends to a building when constructed using any of the methods described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Selected embodiments of the invention will now be described by way of non-limiting example with reference to the accompanying diagrammatic drawings, in which like reference numerals designate like features correspondingly throughout.

In the drawings, which are not drawn to scale:

FIG. 1 shows, schematically, a plan of a building system according to the invention;

FIG. 2 shows, schematically, a cross-section of a wall panel comprising an insulating former and a reinforced concrete rib;

FIG. 3 shows, schematically, cross-sectional views of different configurations of insulating formers;

FIG. 4 shows, schematically, a side elevation of a building constructed using the building system according to the invention;

FIG. 5 shows, schematically, a cross-sectional view of an external wall, floor and roof of a building constructed according to the invention, having a water reservoir built into the roof;

FIG. 6 shows, schematically, a cross-section of a building according to the invention, which has the configuration of a mobile structure and which includes a bunk bed;

FIG. 7 shows, schematically, a plan of the building as shown in FIG. 6, with bunk;

FIG. 8 shows, schematically, a side elevation of a double storey building according to the invention;

FIG. 9 shows, schematically, a cross-sectional view of selected detail marked “IX” in FIG. 8, illustrating the mode of connection of wall panels to a first suspended floor of a double storey building;

FIG. 10 shows, schematically, a cross-sectional view of a portion of a concrete frame structure having upper and lower slabs or suspended floors connected by infill walling, illustrating detail of the mode of attachment of the infill walling to the lower slab;

FIG. 11 shows, schematically, a cross-sectional side view of a special application of the building system of the invention, forming a pitched or sloped roof;

FIG. 12 shows, schematically, a front elevation of an intermediate structure typically used during construction of a building according to the invention, the front wall of the building being braced or supported by a temporary support structure;

FIG. 13 shows, schematically, a front elevation of the building of FIG. 12 after it has been completed to form a mobile structure, and illustrates a continuous lintel extending the full length of the front wall;

FIG. 14 shows, schematically, a front elevation of an elongated building having a continuous lintel made up of three separate polystyrene lintel formers or sections connected by a continuous concrete rib;

FIG. 15 shows, schematically, an end elevation of the building of FIG. 14, having a gable comprising a pair of matched trapezoidal lintel formers arranged to mirror each other;

FIG. 16 shows, schematically, a cross-sectional front elevation of a door manufactured in accordance with the invention, comprising a polystyrene sheet or panel embedded in a reinforced concrete casing; and

FIG. 17 shows, schematically, a cross-sectional end view of the door illustrated in FIG. 16 together with a formwork used in the manufacture of said door.

MODES FOR CARRYING OUT THE INVENTION

Referring to the drawings, reference numeral 10 indicates generally a building system according to the invention. The system 10 includes a plurality of insulating formers 12, each former having a body portion 14 which is preferably manufactured from expanded or extruded polystyrene foam. Those skilled in the art will, however, appreciate that other suitable insulating materials can be used, such as other polymer foams (e.g. polyurethane foam) or compositions like cement-bonded wood fibre or cement-bonded polystyrene beads.

The body portion 14 of the former 12 has a rib-former 16 comprising three internal walls. The rib former 16 defines a rebated portion 18 in which concrete can be set, thereby to form a concrete rib 20. The cross-section of the rib-former 16 can be shaped in a dove-tail fashion so that the rebated portion 18 (and therefore the rib 20) takes on an elongate dove-tail shape. This helps to stop the concrete rib 20 from falling out of the former 12.

Each former 12 has engagement means 22, 24 on either side, for engaging or interlocking with complementary engagement means 22, 24 on the sides of other formers 12. This enables adjacent formers 12 to be located and aligned in register with one another and also provides for front impact load sharing and improved resistance to water penetration.

In the embodiments shown in the drawings, the engagement or interlock means 22, 24 comprise a wedge-shaped rebate 22 on one side and a complementary wedge-shaped formation 24 on the other side of the former 12. Other types of engagement or interlock formations fall within the scope of the invention, for example tongue-in-groove formations, “Lego”-like stud & socket formations, or the like. These are not shown in the drawings.

The concrete rib 20 is typically reinforced. For walling applications the reinforcement may be provided by two lengths of rebar 26 cast into the concrete and mutually spaced from each other. Other methods of reinforcement can be used depending upon the application. For roofing and flooring applications, for example, the reinforcing may be provided by mesh or lattice reinforcement.

In combination, an insulating former 12 and a concrete rib 20 are referred to herein as a “structural unit.” Structural units can take different forms depending upon function. For example, structural units can serve as wall panels 27 (including infill wall panels and cladding panels), lintels 40, roof panels 42, suspended slab panels 42, floor or base panels 44, posts 36, 38, beams, columns, staircases and the like.

Referring to FIG. 3, the wall panels 27 may be sub-divided into standard panels 28; left and right corner panels 30, 32, 34, 35; left and right end posts 36, 38 (to lie flush against door and window frames); etc.

The rebated portion 18 of each former 12 is sometimes located in the middle of the former (suitable for standard wall panels 28) and sometimes shifted more towards one end or the other (suitable for door-posts 36, 38 or corners 30, 32, 34, 35). Also, a single former 12 can define several rebated portions (not shown) so that the resulting panel can contain two or more concrete ribs 20.

The rebated portion or rib former 18 of a former 12 can also be extended to provide a wider concrete rib 20 (useful for corners). The corner panels 30, 34 shown in FIGS. 1 & 3 have this configuration.

It will be appreciated that a wide variety of other configurations can be used for the formers 12.

Typical measurements for standard wall panels 28 are 300 mm width (at the faces) and 100 mm thickness. After plastering, the thickness of a wall 46 is typically therefore 120 mm (taking into account a 10 mm layer of plaster 47 on each side).

Other exemplary variants for wall panels 27 have respective widths of 275 mm, 277 mm, 290 mm, 350 mm and 460 mm. It will be understood that the width may be selected dependent upon the application and design of the building to be constructed.

Similarly, the height of the various wall panels 27 depends upon the height of the wall concerned or the need to accommodate window frames. For example, standard wall panels 28 can be cut to length to serve as window panels as seen in FIG. 4 and FIGS. 12 to 14.

A method of constructing buildings using the system and method of the invention will now be described. Reference will be made to single and double storey buildings.

Offsite Manufacture of Formers.

Data for polystyrene formers 12 are extracted from the structural drawings for a given building and the formers 12 are manufactured to specification, cut to the required shape and length, and marked at a factory off-site (not shown). The manufactured formers 12 are delivered to the site of construction.

Strip Footings.

The soil over the construction area of the building 48 is carefully leveled and foundation trenches 50 for strip footings 52 are excavated. A bed of river sand is laid at the base of the trenches and concrete is cast over the bed, forming a base layer. A grid or mesh of rebar (not shown) is set into the base concrete.

To serve as a slot-former or groove-former (not shown), a length of polystyrene of rectangular section is placed on top of the base concrete along the centerline of the strip footing 52. Although polystyrene is conveniently used as the material for the slot-former because it is cost effective, it will be appreciated that numerous other materials are suitable for this purpose. Typically, the polystyrene slot-former has a depth of 130 mm and a width equivalent to the width of each wall panel 27, plus 5 mm for clearance. In a preferred embodiment, polystyrene slot-formers are used which are 130 mm deep by 105 mm wide by 3000 mm long.

The trench around the polystyrene slot-former is filled with more concrete. Once the concrete has set the slot-former is removed leaving a slot 54 into which individual wall panels 27 can be inserted.

Where the plan of a building specifies curved or circular footings (e.g. those required for rondavels) a composite slot-former can be assembled from a plurality of elongate, flat polystyrene sheets (not shown), each thin enough to conform to the required curves of the building. A stack can be formed from adjacent such sheets arranged on their sides and abutting one another. The stack can be manipulated until it defines the required curve, fixed in that shape either temporarily or permanently, and trimmed to length. In this way a composite laminate of multiple sheets of polystyrene is formed matching the curvature of the footing, and this is used as the slot-former.

A covering is usually wrapped around part of the slot-former (or around the stack of flat sheets) to serve as a release agent. For example, a plastics sheet material may be wrapped around the slot-former to facilitate its release after the concrete has set. In other embodiments, the polystyrene slot-former is pre-treated with a sealing product such as “Duraslurry” to improve water resistance of the concrete at the slot faces.

Typically a completed strip footing 52 for a house measures 200 mm deep by 400 mm wide. Strip footings can generally be made smaller than those needed for equivalent brick- or block wall constructions, due to the lighter weight of the building that results.

In other embodiments of the invention (not shown), precast concrete blocks can be used for the footings instead of concrete that has been cast in situ. Trenches are excavated and leveled with river sand and the concrete blocks are laid on the sand to form the footings.

Walls.

The pre-manufactured polystyrene formers 12 for each wall are laid out on a generally level area on-site. To manufacture structural units such as the wall panels 27, reinforcement 26 is first laid into the rebated portions 18 of the polystyrene formers 12. The reinforcement is typically laid on cover blocks (not shown). Conveniently, two mutually spaced lengths of reinforcement rod or rebar 26 can be used as the reinforcement, for example 4 mm galvanized iron rods. Wire ties can also be used. The reinforcement in the ribs and the thickness of the ribs can be varied, depending on requirements related to load and wall height combinations.

As can best be seen in FIG. 5, at least one of the reinforcement rods 26, and typically both rods, is/are made to project out of each former 12, usually at top and bottom ends 56, 58 of the former. The projecting ends of the rods 26 are cast into a concrete floor slab 60, roof slab 62, and/or lintels 40. The rods 26 can be bent at generally right angles out from the formers 12 so that, in use, they will project into the spaces where the relevant floor slab 60 or roof slab 62 will be cast.

Turning back to the manufacture of the wall panels 27, after the lengths of rebar 26 have been placed, concrete of the required strength is packed into the rebated portion 18 of each former 12 and compacted by hand to form the concrete rib 20 of each panel 27. The concrete used for the rib 20 typically has a compression or crushing strength of approximately 25 MPa.

Once the concrete has set to form the finished wall panels 27, the panels can be erected to form the walls 46 of the building 48.

The bottom ends of the wall panels 27 are first treated against damp, for example by applying two coats of a suitable product such as “Bituseal” to the lower 130 mm of each panel 27. The panels 27 are then inserted vertically into the slots 54 in the footing 52 and braced occasionally near the top to keep the panels upright and to maintain plumbness. Bracing can be performed using props, planks, rods, or the like (not shown) made to lean against the panels. Instead or in addition, steel ties bent into staple shapes (not shown) can be used to pin adjacent panels 27 together.

As can best be seen in FIGS. 1 & 7, the wall panels 27 are erected in such a manner that the concrete rib 20 of each panel faces inwardly, that is, towards the interior of the building. This provides a regularly spaced series of hard concrete surfaces at 300 mm centres to facilitate fitting of internal fixtures and fittings, appliances, sanitaryware, furniture, shelves and the like.

In one embodiment of the invention, special wall panels 36, 38 are used next to the door frames 64 and window frames 66. These panels, which are referred to herein as door posts and window posts, have a reduced width (and/or have the concrete rib 20 shifted off-centre) so that the rib 20 lies closer to the frame. This arrangement facilitates fixing of the frames 64, 66 to the posts on either side. Examples are shown in FIG. 3. The door- and window frames 64, 66 are typically anchor bolted to the concrete ribs 20 of the posts 36, 38.

The posts 36, 38 reach as high as the top of the door- or window frames 64, 66 next to which they stand. Each post has a reinforcement rod or rebar 26 projecting up out of it. During construction this rebar 26 is cast into a lintel 40.

The sequence of erection of a building 48 typically commences with a corner panel (e.g. 30), followed by standard wall panels 28 and door- and window posts 36, 38. Shorter standard wall panels 28 (referred to as window panels) are used under windows and their widths can be made to suit the width of a given window.

In preferred embodiments of the building system there are no special posts 36, 38. Rather, the wall panels are kept substantially uniform (i.e. undifferentiated). This is preferable for purposes of simplicity and cost-effectiveness. As seen in FIGS. 12 to 15 the wall panels used next to the doors and windows are not specially configured but are of the same type and configuration as the remainder of the wall panels. Unlike in the case of the posts 36, 38, these panels do not have concrete ribs specially located for bolting to the frames 64, 66. Instead, as seen in FIG. 13, the door- and window frames 64, 66 are fixed to the concrete of the lintels 40, window panels 28 and floor slabs (not shown in FIG. 13).

As shown in FIG. 13, anchor bolts 102 are used for fixing the door- and window frames 64, 66 to the concrete in each case, except at the bottom of the door frame 64 where 150 mm long nails 103 projecting from the frame 64 are cast into the floor slab.

Channels and rebates (not shown) for electrical conduiting and plumbing, and cavities for plug boxes and other electrical and plumbing installations, can be cut into the polystyrene of the wall panels 27 before plastering.

Internal walls (not shown) can be erected in much the same way as the external walls 46. A product such as “Duraslurry” can be painted over the lower end portions of the internal wall panels, covering the last 100 mm, to protect against water penetration.

In one embodiment of the invention, illustrated in FIGS. 6 & 7, occupancy of the finished building 48 can be increased by mounting one or more bunks 68 on the concrete ribs 20, accessed by a ladder 70. In such an embodiment the ceiling 72 and roof slab 62 are typically designed to be higher than normal to create more internal space for the bunk 68 and persons sleeping on it. The wall panels 27 are therefore made taller.

The bunk 68 can be mounted in a corner formed by two adjoining walls 46. The supporting surface of the bunk 68 may be made from 18 mm shutterboard or 4 mm steel plate supported on cold-formed steel joists, e.g. 75 mm×50 mm joists.

The bunk arrangement is particularly suitable for high-occupancy, low-cost housing. The example bunk 68 shown in the drawings extends 1800 mm into the room and can provide sleeping space for three children (or space for storage).

Ground Floor.

As can best be seen in FIG. 5 a standard concrete floor slab 60 can be cast directly on the ground.

Instead, as shown in FIG. 6, a “composite” floor or base slab 60 can be manufactured. To this end, floor or base panels 44 are laid out in abutment with one another, transverse reinforcement is placed over them and a 30 mm deep concrete topping 61 is cast on top. The composite floor slab 60 has the advantages of providing an insulated floor and enabling building construction to be carried out in the factory rather than on individual sites. The composite floor slab is therefore useful for mobile structures (discussed further below), where a building is manufactured offsite and then transported to its permanent location.

A configuration similar to that of the composite floor slab 60 may be used in the erection of a suspended floor, e.g. the suspended floor or floors of a multi-storey building. (Please refer in this regard to FIGS. 8 and 9 and the discussion below on “Double storey buildings.”)

Preferably, the floor or base panels have the same shape and configuration as the standard wall panels 28. In other words, the wall panels 28 can be used interchangeably as floor or base panels, and as “slab panels” in the composite slab embodiment.

However, in a different embodiment of the invention the floor or base panels 44 are not the same component as the standard wall panels 28. Firstly, their concrete ribs 20 may be designed to have a rectangular rather than dove-tail profile (there being less need to prevent the ribs 20 from falling out of panels intended to be laid flat on the ground). A second difference is that the sides of the floor panels 44 in this alternative embodiment do not have engagement means for engaging with neighbouring panels 44.

The formers for the panels 44 in this latter embodiment may define deep, elongate grooves or slots measuring 100 mm wide×50 mm deep. The panels 44 may be 70 mm deep×300 mm wide.

In all embodiments reinforcement rods 26 or wire ties are made to project from the wall panels 27 and these are concreted into the floor or base slab 60 so that the wall panels 27 and the slab 60 are rigidly fixed to one another.

Roofs and Suspended Floors.

Where specified, a roof 74 can be erected using roof panels 42 and other roof components. For double storey buildings 76 a suspended floor 78 can be erected in a similar way (see FIGS. 8 and 9).

The roof panels 42 preferably have the same shape and configuration as the standard wall panels 28, that is, they are the same component by design. Wall panels 28 thus typically serve also as roof panels 42 (and as floor, base and slab panels).

To erect a roof, polystyrene roof panel formers 12 of required thickness, which have been manufactured in the same way as the wall panel formers 12, are placed on a level surface on-site. Lattice reinforcement is placed on cover blocks (not shown) in the rebated portions, i.e. rib formers, 16 of each roof panel former 12. The reason for using lattice reinforcement instead of individual lengths of rebar is to provide stiffening so that the roof panels 42 can span between temporary supports whilst a concrete topping 80 is laid and cures.

Once the reinforcement has been positioned, concrete of the required strength is placed into the rib former 16 of each former 12 and hand compacted.

Temporary supports or scaffolds (e.g. reference numeral 108 in FIG. 11) are placed as required around the building to support the roof panels 42 while they are assembled on top of the walls 46 and during casting of the concrete topping 80.

The roof panels 42 are arranged and interlocked with one another to form a layer of roof panels 42, while being supported on top of the walls 46 and the temporary supports 108. Overhangs 82 can be provided as shown in FIG. 4. Reinforcement rods 26 projecting up out of the wall panels 27 are pierced through the polystyrene of the roof panels 42 and bent over at right angles so that they can later be cast into the concrete of the topping 80.

A grid of rebar or other reinforcement can be positioned over the top of the roof panels 42 before the concrete topping 80 is laid. The temporary supports are removed once the concrete has reached the required hardness.

The topping 80 is treated or covered to inhibit water penetration. A product (“Coprox”) manufactured by Coprox International (Pty) Ltd can be used for this purpose.

The topping 80 can be sloped down to falls for drainage of rainwater.

In a further application of the invention the roof can be cast in situ rather than being assembled from pre-concreted formers. FIG. 11 shows a cross-section of a roof 74 manufactured in such a way. The cross-section of the drawing is taken through the rebated portions 18 defined by formers 12 on either side of a concrete beam 104.

To construct the roof 74 in situ, a plurality of interlocking polystyrene formers 12 are first put in place, supported directly on the structure to be roofed and/or on temporary supports. For example, the formers 12 can be supported extending, on the one hand, between the walls (not shown) of a structure, and on the other hand the reinforced concrete beam 104. The beam 104 is supported temporarily on a wooden plank 106 resting on a scaffold 108. Lengths of lattice reinforcement 26, made to stand up vertically, are then placed into the rebated portions 18 of the formers 12 and concrete is poured or packed over the formers 12 to a depth sufficient to fill the rebated portions 18 of the formers 12 and also to form a layer of concrete above the formers 12, covering the reinforcement 26. This layer then cures to form a concrete topping 80 locked into the formers 12 beneath. The formers 12, reinforcement 26 and topping 80 together establish a composite roof slab. The scaffold 108 can be removed after setting of the concrete, leaving the roof 74 in place.

The concrete beam 104 can be pre-cast or can be cast in situ. If the beam 104 is cast in situ, formwork or shuttering for the beam 104 can be provided by the ends the formers 12 and by the plank 106. Reinforcing rods 26.1 can be arranged in the channel defined by these shutters. The channel can be filled with concrete at the same time as other concrete is poured over the formers 12.

Longer support beams 104 may need to be thicker and may take the form of an upstand beam 110 or a downstand beam (not shown).

The topping of the roof may be treated with Coprox to inhibit water penetration.

The roof 74 can be pitched, i.e. sloped, as shown in FIG. 11. In order to inhibit gravitational sliding of the concrete during curing of the roof slab, an angle from the horizontal of approximately 12° is preferred. Those skilled in the art will appreciate that a range of other pitch angles may be selected.

The roof can serve as a reservoir 84 for water storage. Portions of such reservoirs 84 can be seen in FIGS. 5 & 6. The topping 80 is specially lined with a water-resistant layer. An outlet tap (not shown) is advantageously provided.

Deep polystyrene copings 86 can be fixed or cast into the edges of the roof 74 to serve as a feature. Where the roof 74 is also a reservoir, the copings 86 can extend around the perimeter of the topping 80 to serve as side shutters or stop-ends to dam the stored water.

Instead of a roof made of roof panels 42, a sheeted or tiled roof (not shown) can be installed. In this case wire ties can be concreted into the top of every second wall panel 27 and fixed to timber wall plates (not shown). The wall plates are normally 38 mm×38 mm battens, which are first clamped in place with G-clamps before being connected to the wire ties.

Lintels.

A lintel 40 typically rests over each door and window opening. Each lintel 40 rests on wall panels 27, for example two end posts 36, 38, one on either side of the door or window opening.

The lintels 40 are manufactured in situ. To start the process, a polystyrene lintel former is placed over a door or window opening and bedded on a mortar bed on top of the end posts 36, 38. Lintel formers are not shown separately in the drawings but the cross-section of a lintel former can be seen in FIG. 5, marked with reference numeral 88.

Lintel formers 88 have side walls and a base wall which together define a deep and thin slot or channel with a U-shaped cross-section. They are made of polystyrene and are cut with the required size, length and U-shaped cross-section. They may be pre-cut at a factory off-site. Lintel formers 88 typically have the following measurements: depth equivalent to the through-depth of the relevant wall panel 27 (e.g. 100 mm); height equivalent to the distance from the top of the relevant door or window opening to the roof 74; and width equivalent to the width of the door or window opening plus the width of the end posts 36, 38 on either side of the opening. The polystyrene side walls (and base wall) of the lintel former 88 are each typically 30 mm deep.

Reinforcement 26 projecting upwardly from end posts 36, 38 pierces through the polystyrene base wall of a lintel former 88 as it is pushed down into place over the door or window opening.

Suitable reinforcement, e.g. a length of rebar 26, is placed in the bottom of the lintel former 88 and supported on cover blocks (not shown). Concrete of required strength is cast in the former 88 and hand compacted. The concrete may be mixed with 9 mm stone.

Tie bars (not shown) can be pushed through the front and back side walls of the lintel former 88 at close enough centres vertically and horizontally to maintain spacing between the side walls, to prevent distortion and to maintain the plumbness of the lintel 40 whilst concreting is carried out. The tie bars can each be sheathed in a PVC ferrule to ease their removal once the concrete has set. U-shaped braces (not shown) of 6 mm diameter bars can be fitted over the top of the lintel former 88 to hold its side walls in place and G-clamps or other appropriate bracing may be secured against the wall panels 27 and lintel formers 88 to hold them in alignment with one another temporarily while the concrete sets. In one embodiment of the invention the lintel former 88 is manufactured so that it has a through-depth greater than that of the wall panels 27. This arrangement allows one polystyrene wall of the lintel former 88 to be removed once the concrete inside has set, leaving an exposed concrete face flush with the wall panels 27. Alternatively, the polystyrene wall can be left in place as an overhanging feature. For example, where 80 mm thick wall panels are used the lintels may project or overhang 20 mm at the external face (not shown).

In preferred embodiments of the inventions, shown, for example, in FIGS. 13 to 15, the lintels 40 can each extend the full length of an external or internal wall. They can also form a continuous “ring beam” running around a building or a room and connecting back to the point of origin to form a closed loop.

The concrete rib (not shown) in such embodiments is formed by means of a continuous pour into the slot defined by several polystyrene lintel formers 88 laid end-to-end. The polystyrene formers 88 make up separate sections while the concrete rib runs continuously through all of them. Reinforcement ties (not shown) can be placed or cast into the lintel rib at any desired location for connecting to the roof. This has advantages over other embodiments of the invention which rely on “short” lintels. There the builder does not have free rein but is restricted to positioning roof ties as dictated by the spacing of concrete ribs in the wall panels.

A further advantage of the “continuous lintel” embodiment is that the wall panels 28 can all be configured to rise to the same height above the ground (typically to the top of the door frames 64 and window frames 66).

In order to create a ring beam, a continuous lintel slot is needed to enable the continuous concrete rib to turn corners. To this end, the corner ends of the polystyrene lintel formers 88 can be mitred (not shown).

Referring to FIG. 15, a lintel 40 may have a generally triangular configuration so that it can serve as a gable. It may comprise a pair of counterpart lintel formers 88, each having a trapezoidal shape, arranged in mirror formation. The two formers in combination make up the required triangular gable shape. The concrete rib may extend continuously across the width of the gable, inside the formers 88, and may continue around the building to form a ring beam.

Doors

Turning to FIGS. 16 and 17, a door which can be manufactured in accordance with the invention is indicated generally by reference numeral 112. The door 112, also referred to as a screed door or Polydoor, is made up of one or more sheets or panels of recycled polystyrene 114 cast into a reinforced concrete casing 116. The Polydoor 112 may have dimensions matching those of any standard door (e.g. 40 mm×813 mm×2032 mm).

Typically the polystyrene sheet 114 is sized to allow for a 50 mm margin or border of concrete on either side of the finished Polydoor. Also, the sheet can have a thickness of 20 mm, allowing it to be embedded to a depth of 10 mm front and back in a 40 mm thick Polydoor.

Polydoors 112 can be manufactured on site or in a factory before construction. For purposes of manufacture a formwork 118 comprising wooden shutters 120 screwed to a standard hollow-core door 122 is made up. The formwork 118 is shown in FIG. 17 during the casting of a Polydoor 112.

Hinges 124 and a lock 126 are temporarily screwed to the shutters 120 during manufacture. Although not shown in FIG. 17, most of the screws for the hinges 124 and the lock 126 are left projecting into the formwork 118 for subsequent casting into the concrete. The holes of the lock 126 are taped closed to prevent ingress of concrete.

A shutter release agent e.g. flexible plastics sheeting (not shown) is applied and a 10 mm layer of concrete mix is laid on top of the standard door 122 forming the base of the formwork 118. The concrete is leveled using a plank (not shown) which has nails projecting 10 mm out of it as a gauge. Recycled polystyrene sheet 114 having a thickness of 20 mm is then laid down on top of the layer of concrete mix. Elongate reinforcement rods (No. 6 mm diameter), indicated by reference numeral 26.2, are positioned on either side of the polystyrene sheet or panel 114, running almost the full height of the Polydoor 112. If necessary the lock-side reinforcement rod 26.2 can be bent so that it passes around the lock 126.

Further concrete mix is then filled in over the polystyrene sheet 114 and around its sides up to the level of the top of the shutters 120. The concrete is floated and allowed to cure. The finished Polydoor 112 is removed from the formwork 118.

The concrete mix used for the Polydoor 112 can be made up as follows: 1 part cement: 1 part sifted river sand: 3 parts polystyrene recycled beads: sufficient water to allow screeding.

Finishing

Internal and external faces of the walls 46 are plastered. The plaster 47 forms part of the structural strength of the walls, providing resistance to impact loadings and penetration by sharp objects. To achieve required fire resistance, the plaster must be a minimum of 10 mm thick, and this thickness is normally used although plaster thicknesses up to 20 mm, applied in two layers, can be specified.

The plaster 47 is preferably a ferrocement mix comprising a blend of cement, river sand and plaster sand to achieve a high strength. Preferably the ratio of cement to river sand to plaster sand falls in the region of 2:3:3. This composition is mixed with approximately 300 litres/m³ water to yield the required plaster having a 28-day crushing or compression strength of approximately 10 MPa. As used herein, the term “ferrocement” does not imply the use of reinforcing mesh underlying the ferrocement mix.

A slurry is painted over the wall panels 27 before the plaster is applied.

Tie projections (e.g. 2 mm diameter) extend outwardly from the wall panels 27 and are bent at right angles so that they lie aligned with the plaster layer 47 and become embedded in it during plastering.

Ceilings 72 also receive a plaster coating. Instead, they may receive a thin skim coat.

Other finishes can be applied to the wall panels 27. For example, gypsum boards can be fixed to interior faces, and stucco, brick or other sidings can be applied to the exterior faces. However, plastering with the ferrocement mix is preferred because of its properties of structural strength and fire retardation as mentioned above.

Double Storey Buildings.

As shown in FIGS. 8 and 9, the system of the invention can also be used to build a double storey structure 76. The method used to construct the suspended floor 78 of the upper storey is similar to the method used to construct the roof 74 of a single storey building 48. The panels 42 used for the suspended floor 78 are typically of the same configuration as those used for the roof 74, and follow the configuration of the standard wall panels 28. Reinforcement rods 26 (4 mm in diameter) project out generally horizontally from the wall panels 27 that are situated above and below the panels 42. The rods 26 are cast into a concrete topping 80 that is laid over the panels 42. Thus, two structural units can share a common reinforcement member cast into the concrete of each unit. The topping 80 and the panels 42 together form the first suspended floor 78 of the double storey structure 76.

During construction the wall panels 27 and the panels 42 are braced until the concrete topping 80 has set. The brace means may be removed or left in place permanently. In FIG. 9, brace means in the form of a tie rod or strut 90 are shown extending between the suspended floor 78 and one of the wall panels 27.

Infill Walling for Concrete Frame Structures

FIG. 10 shows an example of the proposed building system applied to the infilling of concrete frame structures, such as the concrete frame structures typically used for high-rise buildings and other multi-storey structures. In FIG. 10 an infill wall 92 is shown erected between an upper slab 94 and a lower slab 96 of a concrete frame structure which is indicated generally by reference numeral 98. The infill walls 92 are made up of wall panels 27 as described herein. A magnified portion of FIG. 10 shows the former 12, concrete rib 20 and reinforcement components 26 of the wall panel 27. Wall panels 27 can be used to replace other conventional types of non-load bearing infill walling, paneling or cladding, for example brick or stone infill cladding.

Steel brackets 100 are provided for purposes of fixing the wall panel 27 to the slab 96 of the frame structure 98. Suitable fasteners 102 are used to fasten the bracket 100 to the wall panels 27 and to the slab 96. The fasteners 102 may take the form of expanding shield anchor bolts, e.g. “Rawlbolts.”

Mobile Structures.

Mobile structures also fall within the scope of the invention. Mobile structures are constructed at the builder's yard or other manufacturing plant then transported on a crane truck and erected on a level, compacted sand bed or concrete slab. It is not necessary to use concrete footings.

The buildings 48 shown in FIGS. 6 & 13 are examples of mobile structures. The walls 46, base slab 60 and roof slab 62 of a mobile structure are made from polystyrene panels 27, 42, 44 with reinforced concrete ribs 20 as described herein, creating a rigid box construction which can be transported.

The base slab 60 of a mobile structure is manufactured in the form of a composite slab, as described in the section headed “Ground floor” above. Wall panels 27 with projecting reinforcement 26 are cast into a concrete topping 61 laid over the base panels 44 and a roof slab 62 is erected as described elsewhere herein.

In FIG. 12, reference numeral 128 shows an intermediate stage or structure in the construction of a building according to the invention. This type of intermediate structure 128 is often used in the construction of mobile structures as described above. Walls 46 according to the invention are fastened to temporary support structures 130 held up by stands 132 (e.g. scaffolds). The support structure 130 in each case can run the full length of a wall 46. Wire ties (not shown) are used to tie the reinforcement bars 26 projecting up from the walls 46 to the temporary structure 130. The walls 46 are braced or supported by the temporary structures 130 until the floor slab (not shown) cures and locks the walls in place. The temporary structures 130 can then be removed allowing lintels, ring beams, roofs, etc. to be constructed above the walls 46.

Tests.

The Applicant arranged tests to satisfy the requirements of the National Home Builders Registration Council (“NHBRC”) of the Republic of South Africa. These included tests relating to structural performance, impact, chisel test, water penetration, condensation, thermal performance, durability, acoustics and fire testing.

The results of the fire test, carried out by the South African Bureau of Standards (“SABS”) approximately doubled the required resistance of 30 minutes.

Advantages

The building system 10 described herein may have various advantages over other methods of construction.

Cost savings can be achieved. Studies by an independent firm of quantity surveyors have shown that structures obtained by the system 10 show substantial savings compared with typical structures having brick or block walls, and sheet or tile roofs. Also, transport costs can be reduced because the manufacturing procedure can be completed on site.

Furthermore, the system 10 may help to meet minimum standards for insulation of buildings. The structural units described herein are “self-insulating”. In a study it was found that a structure according to the present system insulated against heat significantly better than a structure constructed with M140 blocks and a steel-sheeted roof.

The walls of structures built using the system can take on a wide variety of shapes, allowing scope for more complex architectural variation on plan.

The structural units described herein, which form part of the building system, are lightweight and facilitate relatively easy manual assembly.

In roofs, a measure of additional water-resistance is provided by the polystyrene.

The building system described may find application in areas prone to earthquakes. The use of polystyrene creates a relatively lightweight formwork which can be important in resisting seismic forces, while the reinforced concrete ribs establish a connected framework for strength. Reinforcement elements project from wall panels into the floor slab to enhance continuity and rigidity.

A further advantage is the possibility of construction by unskilled or semi-skilled workers. In certain circumstances the method and system may permit “do-it-yourself” construction of a structure. 

What is claimed is:
 1. A building system which includes a plurality of insulating formers, each former comprising: a body portion manufactured from an insulating material and having at least one internal wall which defines a rebated portion in which concrete can be set, thereby to form a reinforcing rib; and engagement means configured for complementary engagement with at least one other former, thereby to facilitate alignment of the formers in register with one another, in use.
 2. The building system as claimed in claim 1, in which the insulating material comprises a polymer foam.
 3. The building system as claimed in claim 2 in which the polymer foam is selected from the group consisting of polystyrene foam and polyurethane foam.
 4. The building system as claimed in claim 1, in which the at least one internal wall defining the rebated portion of the, or each, former further defines a mouth which opens into the rebated portion; and each former is preconfigured so that the shortest distance from one side of the mouth to the other is shorter than at least one parallel dimension of the rebated portion.
 5. The building system as claimed in claim 1, which further includes at least one concrete rib set in the rebated portion of at least one of the formers.
 6. (canceled)
 7. A building constructed using the building system as claimed in claim
 1. 8. An insulating former for use in a system of building, the insulating former comprising: a body portion manufactured from an insulating material and having at least one internal wall which defines a rebated portion in which concrete can be set, thereby to form a reinforcing concrete rib; and engagement means configured for complementary engagement with at least one other former, thereby to facilitate alignment of the formers in register with one another, in use.
 9. A structural unit which includes the insulating former as claimed in claim 8, and a concrete rib cast in its rebated portion.
 10. The structural unit as claimed in claim 9, which is selected from the group consisting of wall panels, infill wall panels, cladding panels, roof panels, suspended slab panels, floor panels, lintels, posts, beams, columns, staircases and doors.
 11. A building which includes a plurality of structural units as claimed in claim 9, each aligned in abutment with at least one other of the structural units.
 12. The building as claimed in claim 11, in which a plurality of the structural units share a common reinforcement member cast into the concrete of each of said units.
 13. The building as claimed in claim 11 which includes at least one wall having at least one lintel supported thereon, said lintel comprising at least one insulating former and a continuous reinforced concrete rib cast into the former and extending substantially the full length of the wall.
 14. The building as claimed in claim 13, in which the lintel defines sloping upper edges and has the general configuration of a gable.
 15. The building as claimed in claim 13, which includes a plurality of lintels arranged non-linearly and connected to one another by the continuous concrete rib, at least one of the formers defining mitred engagement means for engagement with at least one abutting lintel.
 16. The building as claimed in claim 11, which includes at least one bed mounted on the concrete ribs of a plurality of the structural units.
 17. The building as claimed in claim 11, which includes a roof comprising a plurality of structural units serving as roof panels, the concrete ribs of the roof panels being reinforced with lattice reinforcement.
 18. The building as claimed in claim 17, in which the roof panels are supported by at least one suspended reinforced concrete support beam cast in situ during casting of the concrete ribs of the roof panels, and continuous with such concrete ribs.
 19. The building as claimed in claim 17, in which the roof is a pitched roof and in which a plurality of the roof panels are inclined from the horizontal at an angle in the range from 8° to 16° inclusive.
 20. The building as claimed in claim 11, which includes a roof reservoir comprising a plurality of roof panels, a concrete topping cast thereon, and at least one end wall comprising a polymer foam coping. 21-22. (canceled)
 23. A pre-fabricated structure having a roof and floor connected by walls; the roof, floor and walls each including a plurality of structural units as claimed in claim 9 and said structure being loosely mounted on the ground in a manner permitting tool-free movement of said structure. 24-28. (canceled)
 29. A method of building which includes the steps of: shaping an insulating material to define a plurality of insulating formers, each former defining a rebated portion and engagement means for engagement with at least one other former; laying reinforcement into the rebated portion defined by each former; placing concrete into said rebated portions and allowing it to set, thereby to manufacture a structural unit from each said former; and arranging at least two of the structural units so manufactured in abutment with each other.
 30. A method of building which includes the steps of: shaping an insulating material to define a plurality of insulating formers, each former defining a rebated portion and engagement means for engagement with at least one other former; arranging at least two of said insulating formers in abutment with each other; laying reinforcement into the rebated portion of each former; and placing concrete into the rebated portions of the formers and allowing it to set, thereby to form abutting structural units.
 31. The method of building as claimed in claim 29, in which the insulating material is a polymer foam.
 32. The method of building as claimed in claim 29, in which the step of shaping the insulating material to define the formers includes shaping a mouth which opens into the rebated portion and dimensioning the mouth such that the shortest distance from one side of the mouth to the other is shorter than at least one parallel dimension of the rebated portion.
 33. The method of building as claimed in claim 29, which includes at least one additional step selected from the group consisting of: manufacturing a concrete footing by placing at least one elongate slot-former above a concrete base and casting concrete on either side of it, removing the slot-former to define a slotted footing and inserting structural units into said slotted footing; projecting reinforcement from the structural units and connecting at least two of the structural units by means of the reinforcement; projecting reinforcement from the structural units and casting a concrete slab around said reinforcement; placing concrete over the formers to a depth sufficient to form a concrete layer above the formers; and fastening at least one fixture to at least one of the structural units.
 34. (canceled)
 35. The method of building as claimed in claim 33, in which the additional step is the step of projecting reinforcement from the structural units and casting a concrete slab around said reinforcement, and in which the reinforcement is projected operatively generally horizontally from wall panels above and below a proposed suspended floor slab, and cast into said slab.
 36. (canceled)
 37. The method of building as claimed in claim 23, which includes the steps of: providing a frame structure; erecting the structural units between parts of the concrete frame structure; and fastening the structural units to the frame structure. 38-39. (canceled)
 40. The method of building as claimed in claim 30, which includes the following steps for constructing a pitched roof: supporting a plurality of the insulating formers at a pitched angle to the horizontal, each abutting at least one other of the formers; during the step of laying reinforcement into the rebated portion of each former, laying lattice reinforcement into said portions; and during the step of placing concrete into the rebated portions of the formers, placing the concrete over the formers to a depth sufficient to form a concrete layer above the formers.
 41. (canceled)
 42. The method of building as claimed in claim 40, in which the formers are supported on a reinforced concrete beam cast in situ during the placing of the concrete over the formers. 43-57. (canceled) 